<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		
		<script type="text/javascript">
			// typeof() 判断变量的类型
			var v;
			// 只有变量声明，没有赋值，现在的值就是undefined
			console.log(v);// undefined
			console.log(typeof(v));//undefined
			v = 3.14;
			console.log(v);// 3.14
			console.log(typeof(v));// number
			v = "JS";
			console.log(v);// JS
			console.log(typeof(v));// string
			v = null;
			console.log(v);// null
			console.log(typeof(v));// object
			v = true;
			console.log(v);// true
			console.log(typeof(v));// boolean
			
		   var m = "3";//string
		   var n = 3;// number
		   if (m == n) {// 只是判断值是不是相等
			 console.log("m==n");//值相等
		   }
		   if (m === n) {
			 console.log("m===n");//值一样，类型也一样
		   }
		</script>
	</body>
</html>
